This invention relates to a central dictation system and, in particular, to the control of various functions performed during recording and playback operations.
Central dictation systems are known wherein a central record/playback unit is adapted to be individually accessed by any one of a plurality of remote dictate stations so as to record dictated information on a record medium. In such systems, the central record/playback unit can be accessed by only a single dictate station at any given time. While one dictate station is in communication with the central unit all other dictate stations are excluded, or locked out, from also communicating with the central unit.
The advantage of such central dictation systems is that individual dictators need not be concerned with the manipulation of various recording media, nor need they attend to the time consuming task of delivering recording media having dictation thereon to appropriate personnel for transcription. In the typical central dictation system, a recording medium having a relatively large capacity for recording dictation is provided so that received dictation communicated from a remote dictation station is recorded on the medium and can be subsequently reproduced for transcription. In one type of central record/playback unit, the record medium consists of an endless loop of magnetic tape which is driven past a dictation transducing station and is also driven past a transcribing transducing station. These stations are essentially operated independently of each other so that a dictation operation can be performed simultaneously with and independently of a transcribing operation. Thus, such a central dictation system advantageously permits the efficient use of dictating and transcribing apparatus. Moreover, dictated information can be almost immediately transcribed -- an earlier portion of a dictated message being transcribed while dictation still is in progress. A typical prior art central dictation system having an endless loop of magnetic tape is described in U.S. Pat. No. 3,817,436 issued June 18, 1974, and is assigned to Dictaphone Corporation, the assignee of the present invention.
It is preferable, in many applications of a central dictation system, to ensure the confidentiality of a previously dictated message. That is, where plural dictate stations are capable of communicating with the record/reproduce station, a message which has been recorded on the endless loop of magnetic tape should not be made available to a subsequent dictator during a subsequent dictate operation so that the previously recorded message can be reviewed or erased or otherwise distorted.
Since, in a central dictation system, many dictated messages are recorded on a single endless loop of tape, it is sufficient to rely upon a single transcribing operator to transcribe each dictated message. Usually, a message will be transcribed in the exact sequence in which it was dictated. In some prior art central dictation systems, if a dictated message is to be transcribed out of sequence, it often is necessary for the transcribing operator to listen to each dictated message until the desired message is reached. Accordingly, there has been a long felt need to provide apparatus whereby a particular message can be rapidly accessed and transcribed, notwithstanding the particular sequential position of that message.
In central dictation systems of the aforedescribed type, the capacity of the system to record dictated messages is determined by the length of the endless loop of tape. Obviously, a more efficient use of that given amount of tape can be achieved if the tape is advanced at a relatively slow speed during recording and playback operations. Thus, a greater volume of dictation, i.e., a greater dictation time, is provided as the tape speed is reduced. However, as is known by those of ordinary skill in the tape recording art, as the tape speed is reduced, undesirable background noise and tape hiss inherent in magnetic recording applications become more pronounced. Also, the signal-to-noise ratio associated with such low speed recording systems often becomes undesirably low, thereby making it difficult to detect an information signal and resulting in degraded audio reproduction. Hence, there exists a long felt need to suppress such undesired noise intrinsic to low-speed magnetic playback systems.
Also, for those central dictation systems having an endless loop of tape which, of course, must extend between a dictate transducer site and a transcribe transducer site, it is expected that a quantity of dictated tape normally will be awaiting transcription. This quantity of tape conveniently can be stored at a storage location between the transducer sites. However, it is quite possible that this quantity of tape can be exhausted. In that event, the portion of the dictated messsage which is recorded on the segment of tape extending between the transducer sites heretofore has been unavailable for immediate transcription. In prior art systems wherein an operator at the transcriber station has no control over any apparatus associated with the dictation station, it is necessary to defer further transcription until the magnetic tape is advanced from the dictation transducer site during a subsequent recording operation.